NSUserdefaultsにNSMutablearrayを格納する/読み出す ref: http://qiita.com/tomokr/items/3ba8fe9997e3fb52a16f

file0.m

NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
    NSMutableArray *array = [[NSMutableArray alloc] init];
    NSData *data = [NSKeyedArchiver archivedDataWithRootObject:array];
    [ud setObject:data forKey:@"array_key"];

file1.m

 NSUserDefaults *ud = [NSUserDefaults standardUserDefaults];
    NSData *data = [ud objectForKey:@"array_key"];
    NSMutableArray *array = [NSKeyedUnarchiver unarchiveObjectWithData:data];